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>21.4. Database Configuration</A
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><P
>   Recall from <A
HREF="runtime-config.html"
>Chapter 18</A
> that the
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> server provides a large number of
   run-time configuration variables.  You can set database-specific
   default values for many of these settings.
  </P
><P
>   For example, if for some reason you want to disable the
   <ACRONYM
CLASS="ACRONYM"
>GEQO</ACRONYM
> optimizer for a given database, you'd
   ordinarily have to either disable it for all databases or make sure
   that every connecting client is careful to issue <TT
CLASS="LITERAL"
>SET geqo
   TO off</TT
>.  To make this setting the default within a particular
   database, you can execute the command:
</P><PRE
CLASS="PROGRAMLISTING"
>ALTER DATABASE mydb SET geqo TO off;</PRE
><P>
   This will save the setting (but not set it immediately).  In
   subsequent connections to this database it will appear as though
   <TT
CLASS="LITERAL"
>SET geqo TO off;</TT
> had been executed just before the
   session started.
   Note that users can still alter this setting during their sessions; it
   will only be the default.  To undo any such setting, use
   <TT
CLASS="LITERAL"
>ALTER DATABASE <TT
CLASS="REPLACEABLE"
><I
>dbname</I
></TT
> RESET
   <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
></TT
>.
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